This invention is in the field of hollow articles; more particularly, the invention relates to an enclosed, seamless polymeric article having an enclosed baffle.
Hollow, enclosed, seamless polymeric articles are known in the art and can be made by several methods. Methods useful to make such articles include blow molding, slush molding, polymer casting, and rotational molding.
Rotational molding, also known as rotomolding, is used in the manufacture of hollow objects from polymeric material. In the basic process of rotational molding, solid or liquid polymers are placed in a mold. The mold is first heated and then cooled while being rotated, usually about two perpendicular axes simultaneously. Many polymers can be used in the rotational molding process. Polymers commonly used in rotational molding include polyolefins such as polyethylene. It is also known to use polycarbonates, crosslinkable polyethylene, nylon, and other materials. In selecting the rotational molding grade formulation, care must be taken to assure that there will not be thermal degradation during the heating cycle. A general discussion on rotational molding is given in MODERN PLASTICS ENCYCLOPEDIA 1979-1980, Volume 56, No. 10A, beginning at Page 381.
In making hollow, enclosed, seamless articles, there is an outer wall enclosing an inner space. Generally, the inner space is devoid of structural features other than those that can be molded in during the molding process. Specific uses require structural features within the enclosed, polymeric articles. A typical use requiring such a structural feature is baffles in tanks containing fluids. Presently, hollow, enclosed tanks which contain fluids have baffles built into them. The baffles are used to prevent the fluids within the tanks from sloshing around the tank uncontrollably. Baffles are built into metal tanks and then the tanks are closed by suitable means such as welding two pieces of the tank together leaving a seam.
Baffles have been molded into hollow, enclosed, seamless polymeric articles. One method to do this has been to hold a screen across the inside of the mold where the baffle is to be located. The screen is held in position by a means to connect it attached to the mold wall. A problem with both the use of the screen within the article to secure metal baffles is that it provides a wicking path through the tank wall, or communication from within the inside of the hollow, enclosed polymeric article to outside. This wicking effect is undesirable, particularly when using volatile fluids, such as fuel.